Sun's Oldest Twin Identified

Astronomers have identified and begun to study a star more like the Sun than any other solar body currently known to scientists, with one exception: HIP 102152, as it's called, is nearly four billion years older than our host star. As a result, any observations are essentially an opportunity to peer into the future of the story of the Sun, the researchers explain.

Located 250 light-years from Earth in the constellation Capricornus, HIP 102152 is the oldest solar twin known to date at some 8.2 billion years old, compared to the Sun's 4.6 billion years. Thus, by studying it, researchers have gained an unprecedented look into the evolution of star's like our own.

Among the most pressing questions is that of whether the Sun's chemical composition is typical for a star its age, especially in terms of lithium content. Researchers have long been baffled by the various amounts of lithium found in different stars. The Sun, for example, has just 1 percent of the lithium content originally present in the material it formed from. Examinations of younger solar twins suggested that this may be a result of the Sun's age, although a correlation was impossible to pin down -- until now.

Using the UVES spectograph on the European Southern Observatory's Very Large Telescope, the researchers split up the light into its component colors, allowing them to study the chemical composition and other properties in great detail. In doing so, they discovered that HIP 102152 has very little lithium. This means, according to TalaWanda Monroe, the lead author of the paper and a researchers from the Universidade of São Paulo, that scientists "can now be certain that stars somehow destroy their lithium as they age, and that the Sun's lithium content appears to be normal for its age."

Researchers were further intrigued to find that HIP 102152 contains a chemical composition pattern that, while different than most other solar twins, is similar to the Sun's, in that they both show a deficiency of the elements abundant in meteorites and on Earth. Based on this, the study's authors speculate that HIP 102152 may host terrestrial rocky planets, too.